Ground trainer for training aircraft crew members



4 Shets--SheerI 1 C. D. KOECHLING Dec. 20, 1949 GROUND TRAINER FOR TRAINING AIRCIRAFI CREW MEMBERS Filed April 26, 1946 c. a Komm/Ng @-6. lm

mmm/5y IDece 20, 1949 c. D. KoEcHLlNG GROUND TRAINER FOR TRAINING AIRCRAFT CREW MEMBERS 4 Sheets-Sheet 2 Filed April 26, 1946 /A/VEA/TOR l C. U. KOECHL'l/VG A T TOR/VEV Dec. 20, 1949 c. D. Kol-:CHLING GROUND TRAINER FOR TRAININGy AIRCRAFT CREW MEMBERS Filed April 26. 1946 4 Sheets-Sheet 5 kum@ MQON Ubk MS2 Dec. 20, 1949 c. n. KOECHLING @491,653

` GROUND TRAINER FOR TRAINING ARCRAFT CREW MEMBERS Filed April 2e, 194e n 4 sheets-sheet 4 ENG/NE' D/SBLE FUEL PUMP OF F FUEL 'PUMP OFF FUEL PUMP 0F F FUEL PUMP off T4 uw? FG. 4

REDUCTION BOX A TTOR/VEV Patented Dec. 20, 1949 GROUND TRAINER FOR TRAINING AIRCRAFT CREW MEMBERS Charles D. Koechling, Floral Park, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application April 26, 1946, Serial No. 665,025

9 Claims.

, This invention relates to a ground trainer for training an aircraft crew and more particularly to circuits and apparatus for simulating the functioning of the fuel distribution system of a multiengined airplane.

In an airplane of the type which the trainer of the present invention is designed to simulate, that is, in an airplane having four engines, fuel may be pumped to the carburetors of the four engines from four fuel tanks located in the wings and a fuel tank located in the bomb bay. The distribution of the fuel is controlled by a group of selector Valves located on a panel at one of the crew members station or, in this particular case, at the navigators station on the flight deck.

There are five tank selector valves on the panel individualized to the four wing tanks and to the bomb bay tank. Each one of four of these valves, allocated to the wing tanks, has three ports: one, the inlet port to the associated tank; the second, an outlet to the engine fuel supply line of the enginev allocated to such valve and the third a connection with a cross feed line. Each of these valves is so designed that the inlet from the tank and the outlet to the engine may be opened simultaneously by turning the handle so that a red flow band on the panel is uncovered by an arcuate slot in the valve dial to connect the band on the panel marked Tank No. and the band on the panel marked Engine No. With the handle in this position the cross feed port is closed. The handle may be turned so that the inlet port from the tank, the outlet port to the engine and the cross feed port are all open at the same time. The flow band uncovered Iby the dial at this time connects the band on the panel marked Tank No. the band on the panel marked Engine No. and the cross feed band on the panel. Or the handle may be turned to close off the inlet port from the tank leaving the cross feed port and outlet to the engine open. In the latter case the flow band uncovered by the dial connects the band :on the panel marked Engine No. and the cross feed band. In the fourth or Off position of the handle all ports are closed.

The fifth selector Valve on the panel has an inlet port from the supply leading from the bomb bay tank and an outlet port to the cross feed line. Thus when the handle is in one position these ports are both open and the flow band uncovered by the valve dial connects the band on the panel marked bomb bay tank with the cross feed band on the panel. In the other position of the handle both ports are closed.

Fuel is supplied to each engine carburetor through a pump driven by such engine, which pump incorporates therein a relief Valve which permits fuel to be forced around the pump to the carburetor in case the pump fails. Four electrically driven booster pumps, one assigned to each wing tank, are provided to transfer fuel from one Wing tank to another and to maintain pressure in the fuel line in the event of engine driven pump failure. They are used also to augment pressures during take-01T, landing and at high altitudes and in priming operations for starting the engines. Another booster pump is provided to transfer fuel from the bomb Ibay tank to the wing tanks.

Two fuel sight gauges are provided in the navigators station each provided with a three-port, two-way valve so that the tube of one of the gauges may be connected at will to either the outboard or inboard wing tank in one Wing and the tube of the other gauge may be connected to either the outboard or inboard wing tank in the other Wing. Fuel pressure gauges., one for each engine, are mounted on the cockpit instrument panel at the copilots station.

Fuel is drawn from the four main tank outlets through the booster pumps by way of the main fuel lines to the selector valves and thence through the main lines to each engine driven fuel pump and thence to each carburetor. Thus the normal route for fuel flow is from each main Wing tank to each corresponding engine (No. 1 tank to No. 1 engine, No. 2 tank to No. 2 engine, No. 3 tank to No. 3 engine and No. 4 tank to No. 4 engine).

The installation of the cross feed manifold, however, provides a means for diverting flow from the normal tank to engine route so that fuel from any wing tank may be directed to another engine or to another wing tank and the associated engine. By means of the cross feed system fuel from any tank can be cut off from its corresponding engine which can then be fed from any of the other tanks through the cross feed manifold. Flow of fuel from the bomb bay tank is through the bomb bay booster pump, up through the lbomb bay feed line, through the selector valve on the valve panel to the cross feed manifold and thence to the wing tank to which fuel is to be selectively transferred.

It is the object of the present invention to provide means whereby the operations of a fuel system of the character hereinbefore described are simulated.

A further object .of the invention is to pro- 3 vide electrically operated means for simulating the effect of the operation of fuel selector valves on the engines and fuel pressure indicators of an airplane.

A further object of the invention is to provide electrically operated means for simulating the :operation of the fuel gauges of an airplane.

A still .further object of the invention is to provide electrically operated means controlled at an instructors desk for simulating the failures of engines and booster pumps and the exhaustion of fuel from any fuel tank.

These and other objects pertinent 'thereto are attained by the structure .set forth in the appended claims and disclosed inthe following detailed description when read in connection with the accompanying drawing in which: l

Fig. 1 discloses in the lower portion thereof the fuel gauge motor unit for raising and lowering an indicating fluid in the tube of one gauge 'to simulate the -indication of the quantity of :fuel ineither of the right wing tanks, in the upper .portion thereof 'the motor control circuit :for 'controlling such motor unit, and a box shown Ain 'the lower .right portion thereof representing fthe motor unit and control circuit therefor for Iraising and lowering an indicating fluid in the tube ofa second gauge to simulate the indication ofthe quantity of fuel in either of the left wing tanks;

Fig. 2 shows the two fuel quantity gauges and the fuelselector valve panel of an airplane modi- -fied'lto function in accordance with the present invention;

Fig. 3 shows in the left portion thereof relays and circuits controlled from the selector valves of zFig. 2, in the center portion thereof indicat- -ing lamps atan instructors desk for indicating to -the instructorfthe lposition to which the selector `valves'of Fig. 2 havebeen adjusted by a -crew member andin the right portion thereof controls fand potentiometers operable thereby for simulatin'g .the fuelfquantity in each 'of the wing tanks;

.'Fig. 4 shows in the upper left portion thereof fuel pressure motorunits and the control circuits therefor for simulating the creation of fuel pres- :sure inthe fuel feed line to one of the engine ycarburetors of 'an airplane, due to the operation of the engine driven pump and a booster'pump, .in "the flower portion thereof such relays and `circuits which simulate the operation of said one engine, in-the dot-dash rectangle labeled Co- .pilots panel, switches and relays controlled ythereby v'for -simulating the operation of the booster pumps which would be associated'with the four wing tanks and in the right portion thereof lamps, control switches and fuel pressure indicators'at the instructors desk; and

Fig. `5 is a diagram showing how the other figures 'of the drawing should be assembled to fully disclose the invention.

The'fuel gauges and associated valves disclosed in 'Fig. 2 are similar to those actually installed inan airplane except that the fuel line connections thereto are omitted, one of the inlets to each valve being closed by a plug and the other inlet being connected'by a pipe to the Sylphon bellows of the associated gauge motor unit shown in Fig. l, A switch 200 has been added to each valve which is operable to one or the other of its circuit closing positions by a cam mounted on the'valve shaft, dependent upon whether the Valvehandle 202 is moved to a position in which an actual airplane gauge would be connected 1to aright wing tank or is moved to aposition in 4 which the gauge would be connected to a. left wing tank.

Each gauge glass 204 has an indicating uid therein the height of which in the glass is controlled by pressure applied from a Sylphon bellows connected to the gauge valve by a pipe 203 extending to the Sylphon bellows |00 of the associated motor-unit. .One end ofthe bellows |00 is connected to a frame casting |0| to which the pipe 203 connects and the other, or movable end of the bellows, is attached to a rack |02. yThe v:rack |02 meshes with a rack pinion |03 mounted on the shaft |04. Shaft |04 is journaled in bearings |05 and |06 and also has mounted thereona gear |07 driven by a pinion |08 mounted on therotor shaft of the motor M.

For enabling the height of the indicating fluid to be adjusted in the gauge glass 204 to the correct level when either wing tank to which the gauge appertains is full, an auxiliary bellows v|09 isconnected to the framecasting |'0'I fand is adjustable to vary the pressure "in :the pipe 2203 by the adjustment of the screw'I l0.

The motor M is 'of-the reversible shaded-pole type having its main stator `-winding r||-| eenergizable from the source of Aalternating current i i2 under the control of relay A-.ofrthefassocited motor controlcircuit and having'its shaded-pole windings H3 and lld selectively short-'circuited under the control of relay RV| 'off'thermotoreontrol circuit.

Gear il also through thepinionil tdriveszan auxiliary shaft il@ on which .are :mounted 'the slider ofthe vbalancing,potentiometer:lill and the operating cams "Hi8 fand V'| t9 V'of the limit switches L| and L2, respectively. vThe .slider v| of the potentiometer is connected `throughth'e summing resistor Al to the signal input conductor |20 of the associated'motor `control fcircuitfan'd the winding is'bridged :by themesistor |.2'|. The No. '3 winding terminal is ponn'ect'ed ato the grounded mid-tap of 'the :secondary windingiof transformer Tl -and the No. .l -windingterminal is connected through resistor 7|22 to the Y:right terminal of the secondary winding Aof:transformer T|. The primarywinding of transformerlhis energized from the Halternating ,current source |23 and, since the mid-'tap ofthesecondaryr-win'ding is grounded, lpotentials degrees .outf'of phase will appear between vthe mi'd-tapsand the outer terminals of `thefsecondary Winding and as a consequence the winding 'of .poteniometer Pi is energized by a'potentialrepresentedas-xf phase (p2. IThe cams |`|8and lflefaresoposi-tone'd on the shaft H5 that the cam ."|`|8 opensthe contacts of the .limit switch vLI"-wh'en`theslider approaches the No. 1terminalofthe'i'potentiometer winding to releaseirlayiAto'fstop the motor M and the cam A|'I'9 Vopensthe fcontacts of the limit switch L2 to :stopltheimotoriwhen the slider approaches 'the No. f 3 terminal fof the potentiometer winding.

The fuel quantity motor .control circuit .shown in the upper portion `of 'Fig .1 'is of fthe general type disclosed in Patent No. V2,428,767 :granted October lll, 1947;to`Albert-Davis-Gumley-Holden, and, in general, :comprises arst'zdualva'cuum tube VT which serves asa twostagemesistanee coupled amplier to amplifythefcontrolsignal applied tothe control grid .of itsle'ftiunit from the sliderof gain control rheostatlRl whichLis connected to Ainput 'control .conductor 420, and to apply the ampliedrsignal potential `:to the primary winding of step-upinput transformer T2. The ampliedsignal iis impressed from the lower secondary winding of the transformer through the dual diode tube VT2, serving as a full-wave rectifier, upon the control grid of the thyratron tube MI and the signal is also impressed from the upper secondary winding of the transformer upon the control grid of the thyratron tube R. Grid biases are applied to the control grids of the thyratron tubes MI and R from the secondary winding of the lament supply transformer T3 through the dual diode tube VT3 and are adjusted by the grid bias adjusting rheostats R2 and R3.

Tube MI upon ring causes the operation of the motor impulsing relay I which in turn controls relay A to apply power to the main stator winding of the motor M. Tube R, upon firing,

causes the operation of the motor reversing relay RV which in turn controls relay RVI to short-circuit one or the other of the shadedpole windings ||3 or H4 of the motor M to cause such motor to turn in one or the other direction dependent upon whether relay RVI is operated or unoperated.

Cathode heater current is supplied to the ilaments of all the tubes from the secondary winding of the filament supply transformer T3. Anode potential is supplied to the anodes of tube VT! from the H3G-volt battery BI, anode potential is supplied from the (iO-cycle, 1l5-volt source of phase p1 current |24 through the ballast lamp |25, through the winding of relay I in parallel with resistor |26, and through the choke coil |21 to the anode of tube MI, and from the latter source through lamp |25, through the winding of relay RV in parallel with resistor |28 and thence through choke coil |29 to the anode of tube R.

A similar motor unit and control circuit therefor for controlling the level of the indicating fluid in the gauge glass 2ML to simulate the indication of the quantity of fuel in the left wing tanks is provided, but to simplify the drawing this apparatus has been represented by the rectangle |30 in Fig, 1.

To control the fuel quantity motor control circuits of Fig. 1 whereby the fuel quantity gauges may be operated in simulation 0f the measurement of the quantity of fuel in the wing tanks, four fuel quantity controls are provided at the instructors desk. The control 300 is operable to simulate the quantity of fuel in the No. 1 or left outboard wing tank and the controls 33|, 302 and 303 are operable to simulate the 'quantity of fuel in the left inboard or No. 2, the right inboard or No. 3 and the right outboard or No. 4 tanks, respectively.

The control 303 is connected, for example, to a shaft 304 on which is mounted the slider 305 of a potentiometer 306 and the operating cam 301 of an off-normal switch 308. Cam 301 is cut to hold the switch 308 closed in all positions of the slider 305 except when the slider is at the lower terminal of the potentiometer winding to represent an empty condition of the right outboard wing tank. The winding of potentiometer 306 is energized by potential of phase [pl which is applied from the left secondary winding of transformer TI, Fig. l, over conductor 309, through resistor 3 0, through the Calibrating rheostat 3| l, the winding of which is bridged by resistor 3|2, and thence through the winding of potentiometer 306 to ground. Potential of phase p1 derived at the slider 305 of the potentiometer is thus a measure of the simulated amount of fuel in the right outboard tank and is a maximum when the tank is assumed to be full and the slider is positioned at the upper terminal of the potentiometer winding.

If the navigator1 desires to determine the amount of fuel in the right outboard tank, he will operate the gauge valve handle 202B, to the position shown in Fig. 2 whereupon potential will be applied from the slider 305, over conductor 3|3, over the upper contacts of switch 200R, through summing resistor A2 and over control conductor |20 to the input of the fuel quantity motor control circuit for the right wing tank. Or if he desires to determine the amount of fuel in the right inboard tank, he will operate the gauge valve handle 202R to the alternate position whereupon potential of phase gpl will be applied from the slider 3|4 of potentiometer 3|5, over conductor Slt, over the lower contacts of switch 200B. and thence as traced to the input of the fuel quantity motor circuit for the right wing tanks. In a similar manner potential may be supplied from the slider 3|1 of potentiometer SiS, over conductor 3|9, and from slider 320 of potentiometer 32|, over conductor 32?., and thence over a contact of switch 2001i, dependent upon the position of the gauge glass valve handle 2021i, and resistor All to control conductor I3! extending to the fuel quantity motor control circuit for the left wing tanks.

It will be assumed that the navigator has operated valve handle 232B, to the position disclosed and that potential of phase (p1 is thus applied to the input of the fuel quantity motor control circuit for the right wing tanks representative of the quantity of fuel in the right outboard wing tank as determined by the setting of potentiometer 303. This potential is amplied by the tube VTi, is rectified by the tube VT2 and appears as a positive potential on the control grid of tube MI. Tube MI thereupon fires on positive half cycles of the anode potential applied to its anode and causes the operation of relay I connected into its cathode-anode path over a circuit which may be traced from ground over the cathode-anode path through tube MI, through choke coil |21, through the winding of relay I in parallel with the resistor |23, and thence through ballast lamp 25 to the phase el source of potential |26. At the same time the amplified signal potential appears as a potential of phase e2 on the control grid of tube R and therefore the control grid of tube R will be rendered more negative during each positive half cycle of the anode potential applied to the anode of tube R. Consequently tube R does not lire and relays RV and RVI do not operate. Thus upon each energization of relay I a circuit for relay A is established `from battery over the lower contacts of relay I, over the lower back contact of relay RVi, over the contacts of limit switch Ll, and through the winding of relay A to ground. Relay A upon each energization now applies power from the source |i2 to the main stator winding of motor M, over the previously traced circuit. With relay RV! unoperated, the shaded-pole winding H3 is connected into a short circuit extending from ground over the upper back contact of relay RV| and through such winding to ground. The motor M is therefore caused to rotate in such a direction as to rotate the slider lil of the balancing potentiometer P! towards the No. 1 terminal of its winding.

As the slider moves an increasing potential of phase p2 is applied therefrom through resistor `Al to the input control grid of tube VTI which opposes the signal potential of phase el applied ibo-the input of the tubefVTl fr o rn fthegsligdernaof potentiometer 306 and-has a consequencegthepre- .dominantpotential of phase p11 is. graduallyrefduced andthe tube 'MI responds thereto tc ,gradually reduce "the -power impulses vtransmitted tothe motor. M-whereupon ,the motorgslows down. When the slider H1 of the balancing potentiometer has thus beenmoved to a position inawhich the-phase (p2 applied therefrom balancesthe signalpotential of phase pl applied fromthe slider 3050i potentiometer 396 ,at the instructors desk, ythe tube VTi will receive `no `input potential and therefore the :tube MI will cease'tore and the .motor M will stop. The shaft H16 willnow have -beengrotated Ato a position Vrepresentative :of tthe quantity of fuel in the vright outboard 'tank and through the gear 1.611, the pinion .L63 and rack ;l02'-the`Syl-phon bellows 110i) `.will have produced fa vpressure in 'thepipe ZtSR and in the gauge glass ZMRto'move the indicating fluid :in `the "glass Vto al .level vindicative of the quantity of'fuel ,in the right outboard tank.

If it be assumedthat this tank is full, the slider `of ,potentiometer Pl will have been -moved to :the No.1'1 terminal `of .the potentiometer` winding and the indicating `fluid will have been raised to .the upper or 'full indication mark on the gauge glass EMR. If now the instructor moves the -slider3t5 of potentiometer 3% toward the lower :terminal of its winding representative of a diminution of fuel in the right outboard tank,y the balancingpotential cf phase 02 being now greater than the. signal potential of phase (p1 the predominating potential of phase (p2 now applied tothe input tgrid of tube VTi causes tube R to fire, and to thereby operate relay RV and causes tube MI to operate relays I and A to transmit A.power `impulses to the motor M. Relay RV! be- -ing now operated due to the operation of relay RV, the `circuit of relay A now extends over 'the inner lower front -contact of relay RVI, and the Yshaded-pole Winding H4 of the motor is connected into a short circuit from ground over fthe `upper front contact of relay RVI and -through' the winding of tube llll to ground. The .motorr M now runs in a direction to move the slider H1 .of potentiometer 'Pl toward the No. 3 terminal `of its winding thereby reducing the abalancing potential of phase p2 applied to vthe :input circuit of .tube VTI until this potential :balances the new value of the phase p1 sig- :nal potential whereupon the motor Will stop. Through the operation of the motor the bellows flil has now been readjusted to reduce the pressure inthe gauge glass 2EME thereby lowering the 'level of theindicating fluid in such glass .to indicate tthe reduced quantity of fuel in the right outboard wing tank.

The fuel selector valve panel `205 of `Fig. 2 is identical with that. of an actual airplane which the'trainer simulates. Each valve shaft has a valve handle and 1a valve dial secured thereto. The dial has'an arcuate slot therein, such as .the slot 05 in the .dial 2431, and three radially .disposed red bands', Y2li!! .andZHL On the face of the panel and adjacent to .the periphery of :the dial is a red circle .2|2 depicting the No. 4 engine,.a redfrectangle 213 depicting the No. 4 tank and a red depicted cross feed manifold junction 214, each having a red band extending therefrom. The ends of such three vbands extend radially toward the valve -dial 201, are disposed '90 degrees apart, and are joined by an arcuaten-red band 2H, portions A.of whichare exposed ythrough the slot `206 in the .dial when .the Vatlve :handle i208 V-is *turned to its different selection positions. VThese red bands represent fthe paths of Yfuel flow when the-selectorwalve vis-in different Yselection positions. For example, .withithevalve handle 208 in the position shown, the arcuate band 2li is exposed to join the bands `extending from the circle 2|2, from the rectangle EL3 and from Ythe cross feed junction 52M Athereby representing that in such position of the valve handle, the valve on an actual -air- -plane would permit the flow of fuel vfrom the cross feed line to the No. 4 engine and to the No. 14 tank.

.Should the handle 298 be moved tothe left, the arcuate band 2li would be exposed to show only the interconnection vof the bands extending from the circle '2 l2 and the rectangle 2|3, -repre :.sentative .of fuelv flow from the No. 4 tank to the No. 4 Vengine and the closure of the valve port :to lthe cross .feed line, or should the `handle v 2HE vibe `.moved to the right, the arcuate b and 2H would vbe so exposed as to .show only .the'zconnection of the rectangle 2l3 with the cross feed yjunction'Z lll, representative of the fuel flow from the cross feed to the No. 4 engine and the closure of the portto the No. 4 tank.

The other `wing tank selector valves have Vtheir dials 2'i5, '2id and 2li similarly provided with arcuate slots which when the dials are turned, uncover arcuate bands interconnecting engine and tank representations and other bands 259, v229 and 2M representing other branches of the cross feed manifold. The dial `12.22 of the bomb :bay tank selector valve is similarly provided with an arcuate slot EES which in the position .shown uncovers an arcuate red'band 224 extending from the depicted bomb bay tank 225 to the band .226 depicting another branch of the cross feed manifold thereby representative of the connection of vthe bomb bay tank with `the cross feed manifold. When the valve handle Zl is moved .to another position, the arcuate band '228 is covered indica- 'tive -of the disconnection of the bomb bay tank from the cross feed manifold.

Each of the selector valve shafts, for the purposes of the present invention is provided with a cani, such as the cam 228, which is effective to cause the selective closure of one or more sets of Contact springs. Associated with the cam'on the shaft of each wing tank selectorvalve are three sets-of contact springs such as T, T-CFand :CF and associated with the cam 229 on the shaft of the bomb bay selector valve is a single set of Contact springs CF.

YThe sets of contact springs control the circuits of relays disclosed in Fig. 3 which in `turn control the fuelpressure motor units which simulate the production of fuel pressures in the fuel flow lines eitending to the carburetors of the four engines in response to the operation of engine driven fuel `pumps and booster pumps associated withvwing and bomb bay tanks in accordance with the settings of the fuel selector valves. The relays also control the circuits of lamps at the instructors desk `to inform the instructor as to the manner in which the selector Valves are manipulated `to take care of any fuel supply condition which the .instructor may impose bythe operation of the fuel quantity controls Stil, Bill, EQ2 and w3 hereinbefore referred to or by the operation ofbooster ypump failures which the instructor may impose by the operation of switches 46|] to 4633, inclusive, or by. Ythe. operation .of the circuit breaker throwout switchesllli to fill, inclusive.

.Circuit breaker switches 409 to.4l3, inclusive,

are mounted on the panel at the copilots station which the copilot may close to operate relays FBI, FB2, FB3, FB4 and ABP to simulate the starting cf booster pumps associated with the Nos. l to 4 wing tanks and the bomb bay tank.

The fuel pressure motor unit for simulating the production of fuel pressure due to the operation of the fuel pump associated with the simulated No. 4 engine is provided with a reversible alternating current motor 450 which has its stator winding connected across the outer terminals of the secondary winding of transformer T4 and has its rotor winding energizable under the control of relays IFP, DFP, IFPI and DFP! from different portions of the secondary winding of transformer T4. The motor through the reduction gear box 45| drives the shaft 452 on which are mounted the cams 453 and 454 for operating the #Il and I 1 switches and the gear 455 which, through the gear 45E drives the rotor of the transmitting autosyn or synchro-transmitter STR. The transmitter STR is electrically coupled with the synchro-receiver SR which drives the fuel pressure indicator 42! mounted on the instrument panel at the instructors desk and with a similar synchro-receiver (not shown) which drives a similar fuel pressure indicator mounted on the copilots instrument panel.

A fuel pressure motor unit similar to that disclosed would be provided to simulate the production of fuel pressure due to the operation of the fuel pumps associated with the simulated Nos. l, 2 and 3 engines and each such unit would be instrumental in driving other fuel pressure indicators mounted on the instrument panels at the copilots station and at the instructors desk. The other indicators at the instructors desk are illustrated at 418, 4|9 and 420.

Such portions of the circuits which simulate the operation of the No. 4 engine as are deemed necessary to an understanding of the invention are disclosed schematically in the lower left portion of Fig. 4. For a more complete disclosure of such similar circuits, reference may be had to the application of J. J. Lukacs and W. B. Strickler, Serial No. 542,846, led January 2, 1944. Similar circuits would be provided to simulate the operation of the Nos. l, 2, and 3 engines.

The apparatus employed to carry out the present invention having now been described, the functioning of such apparatus to solve different problems will now be discussed. It will be assumed that a flight is to be simulated and that preparatory to the flight, the instructor turns all of the fuel quantity controls 390 to 303, inclusive to positions representative of full wing tanks. It will also be assumed that a full condition of the bomb bay tank is simulated by the operation of control 324.

The navigator first sets the wing tank selector valves of Fig. 2 to their Tank position and the bomb bay tank selector valve to its Off position. As a result of the setting of the valves, circuits are closed for the TI, T2, T3, and T4 relays, the ,circuit relay T4 extending, for example, from ground over the contacts of the T switch closed by the cam 228 in the set position of the valve handle 238, thence over conductor 230 and through the winding of relay T4 to battery. With these relays operated obvious circuits are established over their inner upper contacts for the Tank lamps at the instructors desk corresponding to the several selector valves to indicate to the instructor that the valves have been operated to their Tank positions. The

navigator may also at this time operate the valves associated with the fuel quantity gauges to determine if the wing tanks have their full quantity of fuel. The gauges will function in the manner previously described. The pilot will then close the booster pump switches 409 to 4I2, inclusive, thereby closing obvious circuits for relays FB-i, FB2, FB3 and FB4 in simulation of the starting of the booster pumps associated with the four wing tanks. This would be essential in the operation of an airplane to furnish the necessary fuel pressure at the engine carburetors for priming the engines. The operation of these relays is indicated to the instructor by the lighting of lamps 422 to 425, inclusive.

With these relays operated and fuel supply lines from each of the wing tanks to the carburetors of the associated engines in the operated positions of the fuel selector valves being simulated by the operation of relays TI to T4, inclusive, circuits are established for the BP relays of the fuel pressure motor units of the four engines, representative of the fact that booster pressure in the fuel lines to the engine carburetors is being simulated. For example the circuit of the BP relay of the motor unit of the No. 4 engine may be traced from ground over the upper front contact of relay FB4, over the back contact of relay 4|1, over conductor 426, over the upper contacts of relay T4, over conductor 421, through the Winding of relay BP to battery. With the fuel quantity controls 300 to 303, inclusive, set to positions representative olf full wing tanks, the cams operated by such controls will be operated tocause the closure of their associated sets of contacts thereby establishing circuits for the FS relays of the fuel pressure motor units of the four engines, representative of the fact that fuel is being supplied to the engine carburetors. For example, the circuit of the FS relay of the motor unit for the No. 4 engine may be traced from ground, over the set of contacts 308 closed by cam 301, over the lower contacts of relay T4, over conductor 428 and through the Winding of relay FS to battery.

Upon the operation of both relays BP and FS of the motor unit associated with the No. 4 engine, a circuit for the ST relay of such unit is established from ground, over the inner' contacts of relay FS, over the lower contacts of relay BP and through the winding of relay ST to battery. Relay ST thereupon operates and establishes a circuit extending from ground over its upper front contacts, overthe back contact of relay UL and through the Winding of relay IFP to battery. Relay IFP thereupon operates establishing a circuit through the rotor of motor 454 which may be traced from the ground terminal of the secondary Winding of transformer T4, through such secondary winding to the 25- volt tap thereof, thence through the rotor winding of the motor and over the front contacts of relay IFP to ground and, since the stator winding of the motor is bridged across the secondary winding of transformer T4, the motor will. now operate to turn the shaft 452 in a clockwise direction representative of an increase in the fuel pressure in the fuel line to the carburetor of the No. 4 engine. When the shaft has been rotated to a position representative of a pressure of 17 pounds per square inch, the cam 454 will operate the middle spring of the associated set of contacts to its alternate position thereby establishing a circuit from ground over the inner upper front contact of relay ST, over such carnagences operatedA contacts and through the Winding of relay ULV to: battery'- which relay upon operating locksv tor ground overthe upper inner frontcontactof` relay`V ST and at its; upper back,` contact opens. the previously: traced circuitV ofv relay IFP. Relay IFP thereuponzreleases to` open the rotor circuitlof motor 45.0` and such motor'thereupon comes to rest. The rotation of shaft 452 has alsobeen instrumental through gearsy 455- and 456 in rotating the'rotor.synchrotransmitter STR thereby causingtheisynchroreceiver SR tol operate and. Itof'set the'fuel pressurel indicator 42! atV theL instructors; desk and the corresponding indicatori (not shown): on the copilots instrument panel to indicate a-fuel pressure of 17 pounds. As-soonasV shaft 452 movesffrom normal, or the positionrepresentative-'of zero: pounds fuel pressure; cam. 41.51%permits-the` closure ofthe set of contacts'` associated therewith: thereby` establishing anI obvious circuit for relay-LL.

The fuel: pressureV motor units (not shown)` associated with theNos. 1,.2and 3-engines, function in. a, similar manner/thereby: causing the fuel pressure. indicators M 8; M9: and: 429', at." the ine structor-s desk and` similar indicators on the copilots instrumentpanel to indicate similated fuel-pressures-of 17 pounds'injthezfuel lines eX- tendingtothe carburetorsiof the; Nos; 1., 2 `andrB engines.r

Upon observingy tha-t'there isrfuel pressure for priming each-.ofthe engines; the pilot may now proceed tofstart each ofthe; engines in the usual order ofprecedence; To' starttheNo'; 4 engine, thepilotv closes the ignitionswitch (not shown) -to-the'I Both positiongltherebyf establishing the ignition circuit which' isxsimulated inr th'e trainer by theoperation ofLtherIGL and IGR relays (Fig. 4). He: then operates the priming` switch 451 thereby causing thefoperation of thePRM relay in simulation ofk the: operation; off. the` solenoid operated? valve Von? Vthe carburetor which admits raw-fuel fromy the-carburetor` tothe intake-manifolds ofv the: top. cylinders oftheengine. With relay; LL previously operated representative of the pressure of lfuel= ati the carburetor of theNo. 41- engine',;the operation of relay PRM establishes a circuit 'from' ground-over.A the contacts thereof, over thefinner'lower fronticontact of relay LL and through the-'winding offrelay PRMI- which operates` and; in turn causesfthe operation of relay PRM2 Relay` PRMZ f upon.` operating locks over its; inner: lowerf contacts' toground at' thef lower back contacty of relayl EST If.

When the? starter'switch-.lnot shown) is now operated, and the turning" overv of-` thel engine underv4 the.V starter 'control is simulated,` the relay RPM becomes= operated,` establishes `an obvious circuit for theI-RPMfrelay 45tin vthe fuel pressuremotor'unitNo'. 4i engine-and;- with the engine primed as represented byf the operated relay PRM2 rand. furnished` with Vignitionas represented by.- the' op'eratedf relaysrIGL land* IGR, aV circuit is establishedffor'relayz This. circuit may be tracedfrom ground; over' the contacts of relays IGL and IGR; over contacts ofI the engine disablekey 4'50fat1the instructors desk, over the lowercontacts:ofz'lrelay LL, over the lower contactsof-relayfPRMZ; overthef upper contacts of relay RPMa-n'd through-the winding of relay EST tobattery.V Relay EST operatesrto simulate the starting of' theengineand` causes` the operation of relay-ESTI; which in turn causes the operation of the EST'relayr459fin the'ffuel pressuremotor unit for the No;,4zengine: Relay'ESTIi also opens the locking circuit of lthePRMZ:relay-which now re'- 12 leases lsince itsinitial operating circuit was opened bythe releaseof relays PRM and PRMI when the pilot released the momentarily' operated" priming switch 451.

The release-of relay PRMZ,Y would release relay EST and therefore, to maintain the simulation of'thelengine as running under throttle control, it isnecessaryforthev pilot to operate the mixture control (not shown) from the idle cut-off position in which relay ICO-l Vis operated to the automaticv rich position in whichA relay ICOI is released. The release of relay ICOI thereby bridges the lower contacts of relay PRMZ, thus maintaining' an operating, circuit for relay EST whereby it islheldl operated and maintains relay ESTI operated;

Relay ST `of the fuel pressure motor unit'is now held operated irrespective of the continued operation of relay BP over a circuit which may be traced from ground, over the outer contacts of relay FS;v overthe contacts. of the EST relay 459. over the contacts of;- the RPM relay 48 and through the winding ofrelay ST to battery and continues tol remain' operated so long as the en'- gine is operating undertlirottlecontrol as'will be represented by theA continued` operation of both relaysv 458. and 4591' If .the engine. is turned oil? when the airspeed of thei simulated flight isf in eXcessof 50 knotsrth'eASzrelay 461' of the engine control circuit will be operated. The EST` relay 45d' will release but the RPM relay 458 will continueto bei operated since the simulated engine will1 beassumed. to be turning over due tothe windmilling action-of its propeller. With the relayA 4dr-andi relayl 458 operated, the circuit of relay 'ST isst'illV established fromgroundover the outer-contactsofrelay FS; over the contacts of relay 45|, the contacts of 'relay 458 vand through the winding of-"relay ST to battery.

The simulation of the starting of the other engines is accomplished-inthe manner just described for' the No. 4Iengine. After take-off of the" flight has been accomplished, the booster pump switches 409 to` 42127,l inclusive, may be opened, thereby causing the release of the BP relays in the fuel pressure motor units.

Controls are provided at the instructors desk by means of which the-instructor may increase or decrease the fuel pressure; If the instructor operates they control 4(33to the DEC position to 'decreasey the fuel pressure in the fuel line to the carburetor ofthe- No. 4 engine, a circuit is established from ground thereover, over the upper contacts of relay LL andthrough relay DFPI to battery thereby causing'the latter relay to operate-to establish a circuit form the Y2li-Volt tap of the secondary winding of transformer T4, through the rotor circuit of rthernotor 450, over the upper back contacts of relays IFP, DFP and IFPI and over the` front contacts of relay DFPI to the 35- Volttap ofthesecondary winding-of transformer T4; The-motor 450wil1 now-run ata slow speed in a directionrepresentative' ofia reduction in fuel pressure soA long as the instructor holds the control 403 closed or if held closed long enough until camv 453 operates the set of contacts associated therewith to release LL and thereby release relay DFPI to stoplthe motor. Theifuel pressure indicators at the pilots station and at the instructors desk will showthe decreasing pressure at a slow enough-rate toavoid attracting the attention of the' copilot too suddenly.

Ifl thel simulated pressure is` reduced below seventeen pounds, the cam 454 releases the contact set-associated therewith.- To bring the pres- 13 sure back t seventeen pounds the copilot should close the booster pump switch 4 l 2 thereby reoperating relay BP. A circuit will now be established from ground over the inner upper front contact of relay ST, over the normal set of contacts of the contact associated with cam 454, over the contacts of relay BP and through the winding of relay ULB to battery. Relay ULB will thereupon operate and establish an obvious circuit for relay IFP which will again establish the previously traced circuit of motor 450 to cause such motor to turn shaft 452 in a direction representative of an increase in pressure or until cam 454 again operates the set of contacts associated therewith to open the circuit of relay ULB and to thereby release relay IFP to stop the motor 45S. While the relay IFP is operated, the operation of relay DFPI by the continued operation of the control 403 at the instructors desk is rendered ineffective. When the fuel pressure has been increased to the desired amount, the copilot restores the booster pump switch 4I2.

The instructor may increase the fuel pressure by operating the control du@ to the INC position in which a circuit is established from ground over the contacts of such control, over the lower contacts of relay ST and through the winding of relay IFPI to battery. Relay IFPI upc-n operating establishes a circuit from the 25mvolt tap of the secondary winding of transformer T4, through the rotor circuit of the motor 45B, over the upper back contacts of relays IFP and DFP and over the front contacts of relay IFPI to the 15-volt tap of the transformer winding whereupon the motor will run at slow speed in a direction to increase the fuel pressure indication so long as the instructor maintains the control Lill operated. The instructor will not cause an increase of indicated fuel pressure in excess of twenty-five pounds.

It will now be assumed that the simulated flight has reached an altitude of 10,000 feet at which the fuel booster pumps should be started. The copilot thereupon operates the booster pump switches 409 to M2, inclusive, thereby causing the operation of the BP relays of the fuel pressure motor units in the manner previously described. As the simulated flight proceeds, the instructor from time to time will adjust the fuel quantity controls Sil@ to 363, inclusive, in a manner representative of the consumption of fuel from the wing tanks. The navigator will, in a manner previously described, check the quantity of fuel in the tanks from time to time.

In the flight of an airplane it may be that one of the engines will consume fuel at a faster rate than the other engines, as for example when it runs at a higher cylinder temperature and the pilot attempts to keep it cool by adjusting its mixture control to automatic rich. This might result towards the end of a long flight in the consumption of all of the fuel in tank normally supplying that engine so that the engine would cease to receive fuel and would slow down to a speed determined only by the wind-milling action of its propeller. To restart the engine it would be necessary to take steps to transfer fuel from one of the other wing tanks to the empty tank. To simulate this condition in the trainer, the instructor .for example, will set the fuel quantity con F trol 333 for the right outboard or No. 4 wing tank to a position representative of a total consumption of fuel from such tank, thereby causing cam 301 to open the set of contacts and thus open the previously traced circuit of the FS relay in the fuel pressure motor unit for the No. 4 engine. Relay FS upon releasing opens the circuit of relay ST which releases and closes a circuit from ground over its inner upper back Contact, over the inner upper contacts of relay LL and through the winding of relay DFP to battery. Relay DFP will thereupon operate and establish a circuit from the 25-volt tap of the secondary winding of transformer T4, through the rotor winding of motor 450, over the upper back Contact of relay IFP, over the front contacts of relay DFP and to the 50-volt tap of the transformer. Motor t! will thereupon rotate the shaft 452 in a direction representative of a reduction in fuel pressure until the cam 453 opens the set of contacts associated therewith to release relay LL whereupon the circuit of relay DFP is opened and the motor stops. The fuel pressure indicator Ml at the instructors desk and the corresponding indicator at the copilots station will now have been set to indicate zero fuel pressure for the No. 4 engine.

The copilot noting the slowing down of the engine as indicated by the tachometer reading and the reduction of fuel pressure will instruct the navigator, for example, to transfer fuel from the left outboard or No. 1 wing tank to the right outboard or No. 4 wing tank in an endeavor to restart the No. 4 engine. The navigator will then operate the fuel selector valve for the Nos. 4 and 1 tanks to their Tank-cross feed positions and the copilot will open the booster pump switch 4I 2 allocated to the No. 4 tank so that the No. 4 tank may be filled from the cross feed manifold. With the engine not firing and turning over only at a speed determined by the windmilling action of its propeller, relay 45S of the fuel pressure motor unit will be released but relay 458 will remain operated.

With the Nos. l and 4 selector valves set into their Tank-cross feed positions, the T-CF switches associated therewith become closed resulting in the establishment of circuits: from ground thereover, over conductors 23| and 232 and through the windings of relays TD4 and TDI to battery. Thereupon such relays operate and close obvious circuits over their lower contacts for the Tank lamps at the instructors desk allocated to the right outboard and left outboard or the Nos. 4 and 1 tanks, respectively, and also close obviousl circuits over their upper contacts for the Cross lamps at the instructors desk allocated to the Nos. 4 and l tanks respectively. The Tank and Cross lamps appertaining to each of these tanks being both lighted, the instructor is apprised of the fact that the Nos. 4

and l fuel selector switches have been operated to their Tank-cross feed positions. With the booster pump switch H2 now opened and the booster pump switch 4&9 still operated, the circuit for relays BP of the fuel pressure motor unit for the No. 4 engine extends from ground over the upper contacts of relays FB! and M41, over conductor 429, over the middle upper contacts of relay TDI, over the inner upper contacts of operated relay TD4 and over conductor 427 through the winding of relay BP to battery.

A new circuit for relay FS is now established from ground over the contacts 323 associated with the fuel quantity control su@ for the left outboard wing tank, over the middle lower front contact of relay TDi, over the inner lower contacts of relay TD4, over conductor 423 and through the winding of relay FS to battery. Relay FS now operates representative of the resumption of fuel supply to the carburetor of the No. 4 engine. At the same timethe. FS' relay of the fuel pressure motor unitfor the No. 1 engine is maintained operated from ground supplied over contacts 323y andi over the: lower middle and inner contacts ofrelay TDI'. With relay BP operated, the reoperation ofjrelay'FS reestablishes the circuit of. relay ST from'ground overv the inner contacts of :relay ES, overA thev lower contacts of relay BP and through'the winding of relay ST to battery. Relay ST now establishes the previously tracedi circuit for: relay IFP over the upper back contact of relay'ULwhich released when relay ST'released andthe shaft 452 rotated to the position representative of Zero fuel pressure and restored the set of contacts` operated by cam 45d toits normal position. Relay IFP now causes the operation of motor 459 until the shaft 452 reaches av position representative of seventeen pounds fuel pressure when relay UL again operates and locks under-the control of relay ST and opens the circuit of relay IFP. The engine should now start as'will be evidenced4 by the tachometer reading. At this time relay 459 will reoperate to establish a-new holding Circuit for relay ST.

The instructor will thenreset the fuel quantity controls 399 andzllS t show a replenishment of fuel inthe No. 4 or right outboard tank and the corresponding diminution of' fuel in the No. 1 or left outboard tank. due to the transfer of fuel from suchy tank to the No. 4 or right outboardl tank. Thenavigator may check the assumed. fuel quantities in these tanks in the manner 'previously` described. Upon the resetting of the control 393 thecontacts are again closed so that when the navigator restores the fuel selector valves allocated to Nos. 1 and 4 tanks to their Engine-tank positions thereby reoperating relays TI and T4 and releasing relays TDI and TD4, thevFS relays of the fuel pressure motor units for the Nos.- 1 and 4 engines are again held operated over the previously traced circuits. At this time the lighted Cross lamps at the instructors desk will become extinguished and all the"Tank lamps will .be lighted to indicate that all of the selector valves are now set in their Engine-tank positions.

Itwill now be assumed that the No. 4 or right outboard tank'loses its fuel supply due to leakage as may be simulated in the trainer by the movement of control 303;to its tank empty position. As previously described, this will result in the release of relay FS of the fuel pressure motor unit for. theNo. 4 engine, the resultant-operation of the shaft of such motor unit to a position representative of the reduction of fuel pressure to zero and the stopping of the engine as will be represented by the release of relay 459. If the copilot is aware of the condition of the No. 4 tank, he will open the booster pump switch 4I2 and` informthe navigator that the No. 4 tank selector. valveshould be set to its Engine-cross feed position and that the No. 1 tank selector valvev should be set to. its Tank-cross feed position, in order that the No.. 4 engine may receive fuel fromthe No. 1 tank over the cross feed manifold while the No. 1 engine continues to receive fuel from the No. 1 tank. With these Valve settings no fuel will be pumped into the leaking No.. 4 tank.

With. the selector Valves set as above described, relay TDI. is operated as .previously described and relay D4 is now operated in a circuit from ground over the=C`F contact set closedby the setting of the No. 4selector valve, over conductor 233 and throughv the winding ofy relayD4 to battery. The

setting of the No. 4 selector valve releasedv relay T4 thereby' extinguishing the Tank lamp and with the D4i relay' now operated a circuit is established over. its inner upper contacts andv through the Cross lamp to battery to inform he instructor that the selector Valve has been reset to its Engine-cross feed position. With relay TDI operated, both the Tank and Cross lamps allocated to the No. 1 tank will light to informthe instructor that the No. 1 selector valve is in its Tank-cross feed position.

The circuit for the BP relay of the fuel pressure motor unit for the No. 4 engine will now be established fromV ground applied by relay FBI:` through the operation of switch les to conductor 42S, thence over the middle upper contacts of relay rTDI', over the middle upper contacts of relay D4 and over conductor. 421 through the' winding of relay BP- to battery. The FSrelay will be reoperated over a circuit from ground over the contacts 323, over the middle lower contacts of relay TDI, over the lower contacts of relay Dfl and over conductor 428 through the winding of relay FS to battery. Relays BP and FS will now function as previously described to cause the fuel pressuremotor unit to function in a manner representative of a restoration of. fuel pressure to theNo. 4 engineV carburetor. The

No. 4 engine should now start and reoperate relay 459 as previously described.

It will now be assumed that the rNos; 2, 3l and 4 wing tanks become empty as would be simulated by the operation ofthe controls 30|, 302 and 303 to their empty positions and the consequent opening of the cam operated contacts controlled by such controls. This would result in the release of the operated FS relays of the fuel pressure motor units for the Nos. 2, 3 and 4 engines and the consequent operation of the fuel pressure motor units to positions representative of the failule of fuel pressure at the carburetors of the Nos. 2, 3 and 4v engines with the stoppage of such engines. Underthis condition the copilot would open all ofthe booster pump switches 409 to 412, inclusive, allocated to the wing tanks, close the booster pump switch H3v to simulateA the starting. of the booster pump. associated. with. the bomb bay tank and inform the navigator to set the Nos. 2, 3 and 4 selector valves andthe booster tank valveinto their Engine-cross feed positions and the No. 1 tank selector Valve into its Tank-cross feed positionin which. all four engines would receive fuel over the cross feed manifold from the bomb bay tank and the No. 1 wing tank.. The closure of the bomb bay booster pump switch. causes the operation of relay ABP which inturn causes the. lighting of lamp 43| at the instructors desk to inform the instructor that the bomb bay booster. switch has been operated.

With the valves thus set the D2, D3, and D4 relays would be operated over circuits established by the closure ofthe TF contacts associated4 with the Nos. 2 to 4 tank selector valves andrelay TDI would be operated over a circuit established. by the closure of the T-CF contact set associated with the No. 1 tank selector Valve. The closure of the contacts associated with the bomb bay tank selector valve establishes a circuit over conductor 234 and through the winding of relay BT to battery. Relay BT operates and. establishes an obvious circuit throughthe Bomb bay lamp.

inner upper contacts for the "Cross lamps to inform the instructor that the Nos. 2 to 3 tank selector valves have been set to their Enginecross feed positions and the operation of relay TDI establishes circuits as previously traced for the Cross and Tank lamps allocated to the No. 1 tank to apprise the instructor that the No. 1 tank selector valve has been set to the Tankcross feed position.

With relays TDI, D2, D3 and D4 operated, a circuit is effective to maintain all of the FS relays operated which may be traced from ground over the contacts 323 associated with the fuel quantity control for the No. l tank, over the inner and middle lower contacts of relay TDI to the FS relay of the fuel pressure motor circuit associated with the No. 1 engine and also over the lower contacts of the operated D12, D3 and D4 relays to the FS relays of the fuel pressure motor units associated with the Nos. 2, 3, and 4 engines. The FS relay of the Ifuel pressure motor unit for the No. 1 engine being thus maintained operated, the fuel pressure unit for that engine will continue to remain in the condition representative of the maintenance of fuel pressure r at the carburetor of the No. 1 engine, The reoperation of the FS relays of the fuel pressure motor units for the Nos. 2, 3 and 4 engines will now cause such fuel pressure motor units to function in a manner representative of the restoration of fuel pressure at the carburetors of the Nos. 2, 3 and 4 engines in the manner previously described. The Nos. 2, 3 and 4 engines should now restart.

It will now be assumed that all of the wing i tanks become empty as would be simulated by the operation of controls 300 to 304, inclusive, to their empty positions and the consequent opening of the cam operated contact sets controlled by such controls. This would result in-l the release of all of the operated FS relays of the fuel pressure motor units and the consequent operation of such units to positions representative of the failure of fuel pressure at the carburetors of the four engines with the resultant.4

stopping of such engines. Under this condition the copilot would open all of the booster pump switches 409 to 4I2 inclusive allocated to the four wing tanks, close the booster pump switch 4I3 to simulate the starting of the booster pump associated with the bomb bay tank and inform the navigator to set the wing tank selector valves and the booster tank selector valve into their Enginecross feed positions.

With the valves thus set the BT, DI D2, D32" and D4 relays are all operated over circuits established by the closure of the CF contacts associated with such valves. The operation of these relays establishes obvious circuits for the Bomb bay and Cross lamps at the instructors desk* to inform the instructor that the selector valves have all been operated to their Cross feed positions to enable fuel to flow from the bomb bay tank to the four engines. With the BT, DI, D2,

D3, D4 and ABP relays operated, a circuit is es-A tablished from ground serially over the outer upper front contacts of relays DI, D2, D3 and D4, over conductor 432, over the lower contacts of relay ABP, over conductor 433, over the inner lower contacts of relay BT, thence in parallel` engine may be traced from the middle upper contacts of relay D4 over conductor 421 and through relay BP to battery. A circuit is also established from ground serially over contacts of relays DI, D2, D3 and D4, thence over conductor 432, over the set of contacts 325 operated by cam 32E of the bomb bay fuel quantity control 324 at the instructors desk, over the lower contacts of relay BT and in parallel over the lower contacts of relays DI, D2, D3 and D4 and through the Vwindings of the FS relays of all of the fuel pressure motor units to battery. For example the circuit of relay FS of the fuel pressure motor unit for the No. 4 engine may be traced from the lower contacts of relay D4, over conductor 42S and through relay FS to battery. Since the FS relays of the fuel pressure motor units are thus reoperated, the motor units are caused to function in a manner representative of the restoration of fuel pressure at the carburetors of the four engines in the manner previously described and the engines should now restart.

The instructor may simulate failure of any of the wing tank booster pumps by the operation of` the corresponding switches 400 to 403, inclusive, to their Fuel pump off position. For eX- ample, to simulate the failure of the fuel pump for the No. 4 or right outboard wing tank, the instructor would operate the switch 403, thereby establishing a circuit over the right contacts of such switch through the winding olf booster pump cut-off relay 4M. The operation of relay 4I'I removes operating ground from the circuit over which the BP relay of the fuel pressure motor unit for the No. 4 engine may be operated thus preventing the operation of such relay when the copilot closes the booster pump switch 4I2.

The instructor may simulate the blowing of any one of the booster pump circuit breaker switches 400 to 4I3, inclusive, by closing one of the appropriate keys 404 to 408, inclusive. For example the closure of key 404 establishes a circuit from full battery through the thermal circuit breaker switch 409 to ground thereby causing such switch to open and to release the associated relay FBI. Relay FBI upon releasing opens the circuit of lamp 422 which becomes extinguished as a signal that the booster pump is not functioning and closes the circuit of lamp 430 which thereupon lights. When the pilot has taken steps to restore the circuit breaker switch, the lamp 430 becomes extinguished as a signal to the instructor that the pilot has corrected the circuit difficulty.

What is claimed is:

l. In a ground trainer for simulating the fuel distribution system of an airplane of a type having a plurality of engines, a plurality of fuel tanks, a fuel pressure booster pumpassociated with the outlet of each of the tanks and a plurality of fuel selector valves through which fuel from the tanks may be distributed to the engines, means for simulating the presence of fuel in each of the tanks, means for simulating the operation of each of the engines, switching means operable in simulation of the operation of the selector Valves, means for simulating the operation of the booster pumps, means associated with each of said engine simulating means for simulating the production of fuel pressure at the carburetor of such engine, means effective to cause the operation of said latter means when said fuel quantity and booster pump simulating means and said switching means have been operated in a manner representative of the supply of fuel under pressure analyses from vthe. tanks to the simulated' engines; and

.means controlled by eachA fuel pressure simulat- -ing means for enabling thesimulation of the starting of the simulated engine with which it 'is associated.

2. In. a ground trainer' for.l simulating the fuel distribution system of an airplane of atype having a plurality of engines', aiplurality of fueltanks, a fuel pressure booster pump associatedl with the outlet of each of the. tanks, and a plurality of fuel selector valvesthrough which fuel from the 'tanks may be distributed to the engines, means for simulating the presence of fuel in each of the tanks, means` for simulating-the .operation of each of the engines, switching means operable in simulation of thel operation: of. the selector valves,

`means forsimulating the operation of the booster tity and booster pump simulating means and said switching meanshavenbeen operated in a manner representative of the supply of fuel under pressureA from the tanks', to the simulated engines, and means controlled by each fuel pressure simulatingv means for simulating. the priming and starting of the simulatedV engine with which it is associated.

3. In va groundtrainer for simulating the fuel distribution system of an airplane of a type having. a plurality of engines, a fuel pressure pump associated with each of the engines, a plurality of fuel tanks and a plurality of fuel selector valves through which fuel from .the tanksv may be distributed to the engines, means for simulating the presence of fuel in each of the tanks, means for simulating the operation of each of the engines, switching means operable in simulation of the operation of thev selector valves, means associated ywith each of said engine vsimulating means for simulating. the production of controlled from theY associated engine simulating means representative of the operation of the engine driven .fuel pump, and means effective to control the operation of said lfuel pressure simu.- lating vmeans "under the joint :control of said fuel .quantity :simulating means., ofv said :switching means and of said engine driven pump simulating means.

4. In a ground trainer for simulating the fuel .distribution system of an .airplane of a type having Va plurality of engines, a fuel pressure pump ,carburetor of such engine, -means controlled from the associated engine simulating means representa-tive of the operation 'of the engine driven `fuel pump, means insaidengine simulating means operable if the simulated :flight has attained` air speed above a predetermined minimum, and means effective .to control the operation Aof each fuel pressure at the ycarburetor of such` engine, -means in each fuel ,pressure simulating means 20 fuel pressure simulating means under the joint control of said fuel' quantity simulating means, of said switching` means and of the enginedriven pump simulating means and of the-air speed simulating means of the simulated engine with which it is associated.

5. In a ground trainer for simulating the fuel distribution system of an airplane of a type having a plurality of engines, a fuel pressure pump associated with each of the engines, a plurality of fuel tanks and ay plurality of fuel selector valves through which fuel from the tanks may be distributed in theV engines, means for simulating the presence of fuel in each of the tanks, means for simulating the operation of each of the engines, switching means Operable in simulation of the operation ofthe selector valves, means associated with each of said engine simulating means for simulating theproduotion of fuel pressure at the carburetor of such engine, means in each of said fuel pressure-simulating means controlled from the associated engine simulating means representative of the operation of the engine ldriven fuel pump and representative of the operation of the engine under throttle control, and means effective to control the operation of each fuel pressure simulating means under the joint control of said latter means, of said fuel quantity simulating means and of said switching means.

6. In a ground trainer for simulating the fuel distribution system of an airplane of a type having a plurality of engines, a fuel pressure pump associated with each of the engines, Aa plurality of fuel tanks and a plurality of fuel selector valves through which fuel from the tanks may be distributed to the engines, means for simulating the presence of fuel in each lof the tanks, means for simulating the operation of each of the engines, switching meansy operable to simulate the operation of the selector valves, means associated with each of said engine simulating means for simulating the production of fuel pressure at the carburetor o-f such engine, a first relay controlled from the associated `engine simulating means when the operation of the ,eng-ine throttle control is simulated, a second vrelay controlled from the associated eng-ine simulating means whenever the simulated engine is rotating either under throttle control or :through the windmilling action of its propeller, a third relay operable under the joint control of saidfuel quantity simulating means 4and of .said switching means and a start relay under the control of said first, second and third relays to' control the operation of said fuel pressure simulating means.

7. Ina :ground trainer for simula-ting the fuel distribution system of an airplane having a plurality of engines, a `fuel pressure pump associated With each of the engines, a plurality of fuel tanks, a fuel pressure booster pum-p associated with the outlet of each of the tanks .and va vplurality of fuel selector valves through Which fuel from the tanks may be distributed to the engines, Vmeans for simulating the presence of f u'elr in each tank, means for Asin'lula'ting the operation of each of the engines, .switching means `operable in simulation of the operation of the selector valves, means for simulating the .operation of booster pumps, means associated with each of said engine vsimulating means for :simulating Ythe production of fuel pressure iatthe carburetor of such engine, an instructors desk, means controlled from said desk to cause saidlatter Vmeans to vop- .erate .toY a Vposition representative of a decrease 21 in fuel pressure, a relay controlled jointly by said fuel quantity simulating means and said switching means representative of the availability of fuel, a relay responsive to the operation of said booster pump simulating means and said switching means representative of booster pump operation and means controlled jointly by said relays to control said fuel pressure simulating means to a position representative of an increase in fuel pressure, said latter means while operated preventing the control of said fuel pressure simulating means from said instructors desk in a manner representative of a decrease in fuel pressure.

8. In a ground trainer for simulating the fuel distribution system of an airplane having a plurality of engines, a fuel pressure pump associated with each of the engines, a plurality of fuel tanks, a fuel pressure booster pump associated with the outlet of each of the tanks, and a plurality of fuel selector valves each operable into one position for associating one engine carburetor solely with a tank allocated thereto, operable into a second position for associating said one engine carburetor and allocated tank With a cross feed manifold and operable into a third position for associating said one engine carburetor solely with the cross feed manifold, means for simulating the presence of fuel in each of the tanks, means for simulating the operation of each of the engines, means for simulating the operation of booster pumps, means associated with each engine simulating means for simulating fuel pressure at the carburetor of such engine, and switching means selectively operable in simulation of the operation of the selector valves to render said fuel pressure simulating means operable under the control of said fuel quantity booster pumps and engine simulating means to represent fuel pressure at the engine carburetors if said selector valves are so set that in the actual airplane fuel would flow from one or more of the tanks to the carburetors of any of the engines.

9. In a ground trainer for simulating the fuel distribution system of an airplane having a plu rality of engines, a fuel pressure pump associated with each of the engines, a plurality of fuel tanks, a fuel pressure booster pump associated with the outlet of each of the tanks and a plurality of fuel selector valves for associating engine carbure* tors with tanks, and with a cross feed manifold or engine carburetors with the cross feed manifold, means for simulating the presence of fuel in each of the tanks, means for simulating the operation of each of the engines, means for simulating the operation of booster pumps, means associated with each engine simulating means for simulating fuel pressure at the carburetor of such engine, and relays selectively operable in the several selecting positions of the valves to render said fuel pressure simulating means operable under the control of said fuel quantity booster pumps and engine simulating means to represent fuel pressure at the engine carburetors if said selector valves are so set that in an actual airplane fuel would flow from one or more of the tanks to the carburetors of any of the engines.

CHARLES D. KOECI-ILING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,446,439 Lieberman Feb. 20, 1923 2,218,546 Muller Oct. 22, 1940 2,423,875 Curtis et al July 15, 1947 

